The primary goal of the proposed study is to identify the brain mechanisms underlying abnormalities in social communication in children. Brain structure, assessed using Magnetic Resonance Imaging (MRI), brain biochemistry, assessed using Magnetic Resonance Spectroscopy (MRS), and social communication, assessed by discourse. repair and thought disorder measures will be compared in three groups of children: 1) children with autistic disorder, 2) children with specific developmental language disabilities (DLD), and 3) age. IQ, socioeconomic status (SES) and sex matched normal children. Specific Aims 1. Using reliable and valid measures of social communication and formal thought disorder, we predict that the social communication deficits in the autistic children will be directly related to severity of the disorder as judged by scores on the ADI. 2. The social communication deficits of the autistic subjects but not the DLD subjects will be associated with structural and functional CNS abnormalities 3. Based on preliminary, results from our pilot study and findings of abnormal cell densities in autistic brains, we predict that we will detect H-1 MRS increases in Nacetylaspartate (NAA) in the frontal lobes of the autistic children, decreases in the choline and myoinositol peaks of temporal lobe areas and increases in the glycine peak of the cerebellum in the autistic subjects but not in the DLD subjects, or the normal subjects. 4. Volumetric measures and grey/white matter ratios of the limbic system and area measurements of cerebellar structures will be smaller in the high functioning autistic subjects as compared to the DLD subjects and the normal children matched by age, IQ, gender and socioeconomic status (SES).